The present invention relates to a pneumatic tire improved in various tire performance parameters, which is effectively reinforced by incorporating a specific short fiber into a rubber member constituting the tire so as to satisfy the basic requirements for a tire.
As a means for reinforcing the rubber member constituting a tire, it has been a common practice to embed reinforcement cords in the rubber or to use a high-hardness rubber. When the rigidity of the rubber member was uniformly changed to improve a specific tire performance, however, a problem occurred that the other tire performance parameters were lowered.
With respect to a pneumatic radial tire, for example, it has been known that road noise can be reduced by enhancing the rigidity of the shoulder portions near the belt edges. It has therefore been a general practice to insert sheets or fillers made of a high hardness compound under both belt end portions to thereby enhance the rigidity of the shoulder portions. When such sheets or fillers made of a high-hardness compound are used, however, the basic performance parameters such as comfortableness in riding and stability in steering are changed by enhancement in the rigidity of the shoulder portions, even though road noise can be reduced.
Further, attempts have been made to enhance selectively the modulus of a rubber member constituting a tire in a specific direction by incorporating a short fiber made of nylon or the like into the rubber member and orienting it in the specific direction. However, the short fibers of the prior art have failed in attaining such effective reinforcement as to satisfy the basic requirements for a tire.